Best stain blocker paint

JohnB47

Having used it myself, I would avoid the spray version of a stain blocker. It creates a cloud of fine white particles that spread far and wide, settle on everything and can't just be brushed off.

I'd go for the brush application version.

MysteryMe

Another Zinsser fan, worked brilliantly on long standing ceiling stains caused by dodgy chimney stack flashing.

What I would recommend is use the cheapest / old brushes and chuck when finished as it is very difficult to clean afterwards. You can get brushes for around a quid in places like Home Bargains etc

casper_gutman

Another vote for Zinsser BIN. It's not cheap, but it really works. I didn't find it particularly difficult to clean the brushes, but it's unusual in that you have to use methylated spirit to clean it up, not water as for emulsion or white spirit which works for oil-based gloss. If you have meths around anyway then try that, but otherwise just buy the cheapest brushed you can get and treat them as disposable, as MysteryMe suggests.